FAO Nutrition Meetings Report Series No. 48A WHO/FOOD ADD/70.39TOXICOLOGICAL EVALUATION OF SOMEEXTRACTION SOLVENTS AND CERTAIN OTHER SUBSTANCES
The content of this document is the
result of the deliberations of the Joint
FAO/WHO Expert Committee on Food Additives
which met in Geneva, 24 June -2 July 19701
Food and Agriculture Organization of the United Nations
World Health Organization
1 Fourteenth report of the Joint FAO/WHO Expert Committee on Food
Additives, FAO Nutrition Meetings Report Series in press; Wld HlthOrg. techn. Rep. Ser., in press.
FOOD-GRADE MINERAL OIL
Biological data
Biological aspects
Mineral oils are of variable composition depending on the boiling
point of the fractions used. For food purposes usually liquid
petrolatum or liquid paraffin are employed which consist essentially
of n-alkanes and some cyclic paraffins. They are chemically inert
especially as regards the straight chain alkanes and on ingestion most
of the mineral oil (98%) remains unabsorbed in the faeces. There is
evidence now that small amounts of mineral oil (2%) are absorbed as
such by the intestinal mucosa and are distributed throughout the body.
A very small fraction may undergo further biochemical transformation.
Sources of mineral oil are laxatives or oils used in food technology
as release agents or for lubrication purposes (Boitnott and Margolis,
1966).
Oil droplets, identified as saturated alkane hydrocarbons, have
been demonstrated in mesenteric lymphnodes and nodes of the porta
hepatis in man. Similar droplets have been identified in human liver,
spleen and adipose tissue. The small amounts formed are consistent
with the calculated intake from food use (47.5 g per head per year in
the US). No known harm appears associated with these residues
(Boitnott and Margolis, 1966).
Similar deposition of oil and minor absorption was demonstrated
in rabbits, rats and guinea-pigs fed liquid petroleum for 7 months or
more. Histochemical evidence showed absorption to be proportionate to
length of exposure. The mechanism of absorption was unknown but the
absorbed particles showed evidence of foreign body reaction and
phagocytic ingestion (Stryker, 1941).
Mineral oil used as emulsifying medium for s.c. injection was
transported from the site of injection without causing any systemic
effects (Brown, 1966).
H3-labelled mineral oil was administered to rats orally and
i.p., 5 hours after oral dosing with 0.66 mg/kg bodyweight it could be
shown that over 80% was not absorbed but excreted in the faeces, 1-5%
was absorbed unchanged and another 15% appeared in carcass as H3
non-mineral oil substance. Some H3 had exchanged with available H and
possibly some mineral oil had been modified metabolically.
Radioactivity was found principally in liver, fat, kidney, brain, and
spleen. Following i.p. administration there was only very slow
excretion. 11% appeared in the faeces during 8 days and only traces in
the urine (Ebert et al., 1966).
Mineral oil passes through the gut wall unchanged and more is
absorbed in the presence of powerful emulsifiers, provided that the
particle size of the emulsion is about 0.5µ (Frazer et al., 1944).
Prolonged administration of 0.66 ml/kg for 31 days had no effect on
the amount absorbed when compared with single dosing (Ebert et al.,
1966).
A wide range of fractions of mineral oil contain carcinogenic
compounds especially higher boiling fractions of the range 300° - 350°
- 400°C as shown by skin painting of mice and rabbits (Cook et al.,
1958) but refined material may be free from these carcinogenic
constituents (Prigal, 1967). Inoculation of 64 mice with a combination
of mineral oil and killed staphylococci induced plasma cell tumours in
7 animals (Potter and Robertson, 1961), Later experiments produced
similar results with mineral oil alone (Potter and Boyce, 1962). Some
doubts have been raised as to the probable role of virus in production
of these mouse plasma cell tumours (Prigal, 1967). No human cancer has
been reported following many years of oleothorax use (Prigal, 1967).
Short-term studies
Rat: 10 rats were each fed a total of 17 g liquid paraffin in 18 g
olive oil over 16 days mixed into their normal diet. Some 65% was
absorbed as estimated free faecal loss. Another 5 rats received over
28 days a total of 28 g liquid paraffin in their diet. Only 9% was
absorbed. Lymph collected during absorption from intestinal lymphatics
showed that absorbed paraffin had been metabolically modified. (Daniel
et al., 1953).
Long-term studies
Mouse: 2 groups of 30 mice had mineral oil applied to their skin 3
times weekly at 15 mg/application for 311 and 478 days respectively.
No tumours were found (Esso Research, 1960).
Rat: Animals were kept for 15 months on diets supplemented with 10%
liquid paraffin. The liver contained 0.4% dry weight liquid paraffin.
Some active metabolism may occur but liver function was not affected.
(Daniel et al., 1953). In another experiment 2% mineral oil was fed in
the diet to 30 rats for 500 days without adverse effects (Schmäghl and
Reiter, 1953).
Nutritional implications
There are two possible reasons for the presence of mineral oil in
food; (1) in trace amounts from its use as a lubricant or separant
e.g. in tin greasing before baking, or from traces on the surface of
knives used to cut dough in breadmaking, or as a coating e.g. of
fruit; (2) as a substitute for fat either because it is cheaper or in
slimming foods. The maximum daily intake is calculated to be about 100
mg of which some 80 mg are contributed from its use on the machinery
in the baking industry (Council on White Mineral Oil, 1961).
There has been a great deal of work on the effect of mineral oil
in impeding the absorption of fat soluble vitamins A (and precursors)
D, E, K and essential fatty acids. There is no doubt that interference
with absorption can occur, particularly of carotene if amounts in food
exceed approximately 6000 ppm (Steigmann et al., 1952). Whether the
amounts likely to appear in the food of children are of clinical
importance is much less certain (assuming that it is not used as an
ingredient as in (2) above). But the diets of many of these may
contain amounts of these vitamins that are in any case marginal or
inadequate and there seems no reason for the inclusion of mineral oil
in foods which are specifically intended for infants with the possible
exception of rusks (concerning which enquiries are being made which
will be later reported as they may be subject to the same
contaminating processes as bread).
Comments
The use of food grade mineral oil is self-limiting because of its
laxative effect. Although a small percentage of ingested mineral oil
is absorbed as such and deposited in various organs it is without any
apparent harm. Most of the ingested material is not absorbed but is
excreted in the faeces. Apart from the nutritional implications in
relation to the intake of fat soluble vitamins, there are no
toxicological problems arising from the use of food grade mineral oil.
Evaluation
There appears to be no need to set a limit in food beyond that of
good manufacturing practice.
REFERENCES
Boitnott, J. K. & Margolis, S. (1966) Bull. Johns Hopk. Hosp., 118,
414
Brown, E. A. (1966) Review of Allergy, 20, 148 & 235
Cook, J. W., Carruthers, W. & Woodhouse, D. L. (1958) Brit. med.Bull., 14, 132
Council on White Mineral oil (1961) Food Additive Petition 302 to US
Food and Drug Administration dated 21/2/1961
Daniel, J. W. et al. (1953) Biochem. 1., 54, 37
Ebert, A. G., Schleifer, C. R. & Hess, S. M. (1966) J. Pharmac.Sci., 55, 923
Esso Research (1960) Unpublished report submitted to WHO
Frazer, A. C. Schulman, J. H. & Stewart, H. C. (1944) J. Physiol.,
103, 306
Potter, M. & Boyce, C. R. (1962) Nature, 193, 1086
Potter, M. & Robertson, J. (1961) J. nat. Cancer Inst., 25, 847
Prigal, S. J. (1967) Annals of Allergy, 25, 449
Schmähl, D. & Reiter, A. (1953) Arzneimittel-Forsch., 3, 403
Steigmann F. et al. (1952) Gastroent., 20, 587
Stryker, W. A. (1941) Arch. Pathol., 31, 670